Two-hoist control



July 30, 1935. HILD 2,009,889

TWO-HOI ST CONTROL Filed Feb. 12, 1934 3 Sheets- Sheet 2 I m'entor July 30, 1935. F, H|| D 2,009,889

TWO -HOI ST CONTROL Filed Feb. 12, 1934 5 Sheets-Sheet 3 I m'cntor .366 I Patented July 30, 1 935 UNITED STATES PATENT OFFICE 22 Claims.

- My invention relates to hoisting apparatus for oil and gas wells and more particularly to that used'for rotary drilling in which the hoisting requirements are quite unlike those obtaining in other industries.

The increase in the depth of oil and gas wells multiplies the mechanical and operating difliculties of hoisting, lowering and feeding the long strings especially in rotary drilling. It is highly important to hold to the minimum the necessary interruptions to the actual cutting of the formation and the circulation of the mud for carrying up the cuttings; hence the need for high hoisting speed to pull out the drill string for change of bits and return the drill into the-bored hole as rapidly as possible. This has necessitated powerful massive draw works and power plant for each derrick; but with load and operating requirements such that the practical utility of certain essential constituents of the installations have not only been reached but often exceeded with resultant breakage, damage and delay.

It is an object of my invention to lessen the excessive loads and stresses on these constituents and at the same time improve and speed up the operations by providing and utilizing two hoists I each with its power plant for raising and lowering the drill string, thereby increasing the hoisting speed and also lessening the mechanical loads and stresses on the entire hoisting systems. The installation in a well drilling derrick of two hoists each with its own power plant is not unusual, but only one hoist is used at any time, the other being alwaysstationary, so that one serves either as a reserve against break down of the active hoist, or occasionally as a feeding auxiliary while the other hoist is held stationary.

When both hoists are operated together with a common load line and a common traveling block the hoisting speed on the drill string is greatly increased being in effect the sum of the speeds caused by the two hoists. Moreover .by adding more loops of the load line to the traveling block, the stresses and speeds of each power plant, each draw works and its transmission and the common hoisting line will be-materially decreased. It is'an object of my invention to accomplish this by providing power operated clutches and brakes with multiple control and operation of the draw works and motive power so arranged that a single operator can safely control and operate both draw works and their respective motors.

A further object of my invention is to provide an automatic safety interlock to prevent closing diagram the arrangement of the clutches at improper times, thereby preventing costly damage to the hoisting plant and avoiding serious delay to the well drilling.

Other objects and benefits of my invention will become apparent upon consideration of the description and accompanying drawings herewith;

Figure 1 shows a derrick with two sets of draw works arranged to embody my invention.

Figure 2 shows in plan and semi-diagram the application of 'my invention to the installation of Figure 1 by means employing compressed air.

Figure 3 shows in diagram an application of the invention'by electro-ma'gnetic means.

Figure 4 shows in front elevation and semiclutches.

Figure 5 shows in elevation the power controlled brake for the hoist drum in alternative arrangement. f

Figure 6 illustrates a three way control valve linked to a pedal or lever' for power control of either a clutch or the hoist brake.

Figures 7 and 8 show the automatic interlock for the draw works clutches.

Figure 9 illustrates the electric control switch and rheostat linked to clutch pedal and to brake 1 lever.

Referring to the drawings, the derrick I I has the crown block I! over which passes the common load line l3 which is threaded throughthe traveling block H for supporting drill string I5. The last named passes through the rotary machine It into the well hole. A draw works I! is placed on one 7 side of the derrick and is driven by the motor l8.

A chain I9 connects the draw works I! with the rotary ii for rotating the drill string. A second draw works 20 driven by motor 2| is placed on a another side of the derrick either opposite the draw works I1 or at right angles thereto. The drill string includes the swivel 22 which is connected by the mud hose 23 to the mud pumps (not shown).

The invention is applicable to any conventional draw works whether of two speeds or eight speeds or any other number. As here illustrated the two speed draw works I! comprises the line shaft 24 and the drum shaft 25, the latter mounting the hoist drum 26. The shafts are connected by sprockets and chains to each other and to reduction gear 21 which is.coupled to motor is. Thus sprocket 28 on the reduction gear 21 is chain connected to sprocket 29 which is secured to line shaft 2i. Sprockets 30 and II secured to the line shaft are chain connected to Jaw clutch floating sprockets 32 and 33 respectively, both of the power operated 15 2 latter being rotatable on drum shaft 25. A sloping jaw clutch 3d splined on the drum shaft may be moved to engage sprocket 32 which is the slow speed drum sprocket. A square jaw clutch 35 splined on the drum shaft may be moved to engage the high speed sprocket 33. ;A rotary drive sprocket with its clutch is on line shaft 2d and connected by chain it to a sprocket on the rotary machine it. Similarly draw works 29 comprises the line shaft 31, the drum shaft 38, the hoist drum at. The line shaft 31 has sprockets ed and M chain connected to the drum clutch sprockets er and 53 respectively which float on the drum shaft 38, sloping jaw clutch id on the shaft may engage the slow speed sprocket 32, and square jaw clutch (it on the drum shaft may engage high speed sprocket 33. A sprocket id on the line shaft 31 is chain connected to a sprocket 51 on the reduction gear it which is coupled to motor 29.

One end of line it is secured to and wrapped on hoist drum 28 or" draw works 61. The other end of the line is secured to and wrapped. on hoist 39 of draw works 2@. The hoist drum as has suitable brake bands for retarding or preventing its rotation; these bands are connected to brake shaft it and operated by brake lever 5d secured to the brake shaft. Similarly the hoist drum 39 has its brake bands secured to brake shaft 5! and operated by brake lever 52.

Clutch 9% of draw works i1 is-yoked to clutch lever 53 which is pivoted at at, and clutch is yoked to lever 55 pivoted at at. A link 5? connects lever 53 to a foot pedal 58 which when depressed as by being stepped on by the driller, will move lever 53 about its pivot and slide clutch 36 into engagement with drum sprocket 32. A spring 59 pulling on lever 53 urges the clutch at out of engagement, as soon as the depressing force on the foot pedal 58 is removed. In like manner the linkage for clutch 35 includes link 59 connecting yoke lever 55 to foot pedal ti, and spring t2. Similarly, for draw works 20 the linkage for clutch id comprises yoke 63, pivot 6d, foot pedal and spring 65a. The linkage for clutch t5 includes yoke lever- 66, pivot 6'8, link $8, foot pedal 69 and spring 69a.

To the generally familiar systems of multiple operation of electric motors I have added and incorporated certain novel and simple features of load limitation and control.

Referring to Figure 2, switch 10 and wires 1! connect a source of electric energy to contactorresistance groups 12 and 13. Group 12 'is connected to motor I8 by stator leads 14 and rotor resistance wires 15. Likewise group 13 'is connected to motor 2| by stator leads 16 and rotor resistance wires 11.

A master controller 18 located at draw works l1 and another master; controller 19 located at draw works 20 are connected to each other and to contactor groups 12 and 13 respectively by a cable comprising the contactor control wires. The master controller and the contactor groups 12 and 13 are provided with suitable cutouts and switches so'that motors l8and 2 I may be operated individually or simultaneously and either forward or backward. The system in this paragraph'described is well known so that more detailed illustration and description are believed unnecessary. .In one of the stator leads 14, I have inserted a series transformer 8| the secondary of which is connected by wires 82 to the operating magnet of a contactor switch 83. The switch members of contactor 83 are inserted into one of a pair of from the aooaese wires fit which lead from two of the stator leads it to an interceptor magnet so as to control the energizing of the interceptor-magnet. The last named is so disposed that when it is energized, its armature 86 is pulled into position to intercept '5 clutch lever 55 and thereby prevent clutch 35 engaging drum sprocket 33. A spring d1 pulls armature 38 into normally open position when interceptor-magnet 85 is not energized and permits free movement of the clutch 35 and its linkage In the operation of hoisting, the driller first starts motor it slowly by manipulating master controller 18 and then quickly steps on foot. pedal 58 which closes slopping jaw clutch 3% into slow speed sprocket 52, thereby rotating drum 5 2B and putting the entire hoisting system and its load into hoisting motion; then he steps on pedal 68 and at the same time removes his foot pedal 58.' When pedal Si is depressed, the clutch 35 engages high speed sprocket 33, the 20 resultant higher speed of drum shaft 26 automatically causes the sloping jaw clutch 35 to be forced out of engagement with slow speed sprocket 32 and pulledfree therefrom byspring 59. This is the normal sequence; but if the load'25 imposed by slow sprocket 33 is already so large that the greater torque imposed by high speed sprocket 35 would excessively overload motor It, then interceptor-magnet 85 is actuated and prevents closing clutch Stiinto the high speed sprock- 30 et 33. This occurs because the current input to motor it is proportional to the load upon it, and when the current in series transformer 8i reaches a predetermined value, the contactor switch 83 'is 95. The compressor set furnishes compressed air 1 to air cylinders which are connected to the clutch and brake linkage, the cylinders being controlled by valves which are operated by the foot pedals 50 and brake lever of one of the draw works. Thus the piston 91 of cylinder 96 is connected to clutch lever 63 at draw works 20. A pipe 98 leads from the cylinder 96 to a. three-way valve 99 which is linked to foot pedal 58 at draw works 11. The 55 three-way valve. is connected by a pipe I00 to a supply pipe it)! which leads from tank 9| to all of the air valves. The three-way valve 99 has a port to the atmosphere. When the pedal 58 is depressedthe valve is moved to connect 00 pipe I00 with pipe It'll so that compressed air from tank 9! is admitted to cylinder 96, whereupon plston 91 pushing against clutch lever 63 moves the clutch 44 into engagement with sprocket 42. Meanwhile the same downward movement 65 of pedal 58 has shifted clutch 34 into sprocket 32 at draw works l1. Upon releasing pedal 58 so that it moves upward, the valve 99 is moved to' close the port to pipe I00 and to open pipe 98 0 to the atmosphere, whereupon the compressed air in cylinder 96 and pipe 98 are discharged to the atmosphere. and the piston 91 urged by the clutch linkage including spring 65a, returns to its initial position and the clutch moves free of 75 the motor 89 by wires 5:

ill)

- sprocket 42.

At the same time the clutch 34 and sprocket 32 are shifted free of each other.

In like manner the piston of cylinder I03 is connected to the linkage of clutch 45 at draw works 33. .A pipe Hi3 leads from cylinder E02 to a three-way valve I34 which. is linked to pedal St at draw works Hi. This three-way valve is connected by pipe I to the common supply pipe NH. The operation is similar to that just described for cylinder 96. The depression of pedal 8| causes the clutch 55 to engage sprocket 43 and at the same time clutch 35 and sprocket 33 at draw works I! are moved into engagement. Upon releasing pedal BI its upward movement results in these sprockets and clutches moving free of one another.

As shown in Figure 6, the pedal 58 for example may have a limited angular movement on a rock shaft lilii which transmits motion to the clutch linkage when the pedal is depressed. This may be done by intercepting jaws Iil'l of pedal 58 and rock shaft Q83. When thedriller removes is foot pressure, a spring ltt urges the pedal through the free angular space between the jaws itl thereby effecting quick opening oi valve 39 and discharging the air pressure of cylinder 36, so as not to hinder the clutch linkage from freeing the clutch.

Referring to Figure 5, aweight Hi3 hung on the end of brake lever 52 of draw works 23 normally holds the brake against the hoist drum 39. A line M3 secured to the brake lever passes around an idler pulley iii, through a pulley block i it and is dead ended on jack post 6 G3. The piston of an air cylinder H3 is secured to pulley block Alternatively in Figure 2, the piston of cylinder 5 i4 is linked to a crank arm or lever of brake shaft 5i to which the brake lever 52 is secured. A pipe II5 connects the cylinder Ht to a three-way air valve lit which is linked to brake lever 50 of draw works ll. The supply pipe illl connects the air valve M5 to tank 99. The valve is similar to those previously described and like them has a port to atmosphere.

When the driller moves brake lever 53 to ease or free the brake pressure on hoist drum lit, the movement of the brake lever is transmitted to the valve lit, which admits compressed air from tank at through pipes NH and M5 into air cylinder lid, whereupon the piston of the air cylinder acting upon the brake linkage at hoist drum 39, correspondingly eases or frees the brake pressure on the hoist drum 39. Conversely, when the driller moves brake lever 53 to apply brake pressure on hoist drum 26, the corresponding brake action is applied on hoist drum 33 by the weight M39 controlled by air cylinder li t and air valve H3.

, In Figure 3, the clutches and brakes are moved to close by electr c-magnets in lieu of air cylinders. Motor H8 which drives draw works it is connected to a suitable source of electrical energy I" by wires II9, power switch 523, wires I122 and rheostat I23. The magnet of a contactor switch I24 is inserted in one of the wires I22 in series with motor H8. Similarly motor I29 which 'drives draw works 20 is connected to the source H! by wires II9, power switch I25, wires I26 and rheostat I21. The magnet of a contactor switch I28 is in series with motor I2I.

For the draw works I? the armature of a magnet I29 is connected to the linkage 60 and 55 which move clutch 35. Likewise the armature of magnet I30 is linked to yoke lever 53 of clutch 34. For draw works 20 magnet I3I is linked to clutch 44 and magnet l32 is linked toclutch #5. A pair of power wires l33 for energizing the clutch and brake magnets is connected by switch I35 to source H1. The circuit for clutch magnet I29 is as follows: switch II35 connects one of power wires 533 to wire 1136 which leads to the switch member of contactor M l, thence by wire it? to magnet I29 then to the common return wire I33 which is connected to the second or return line of power wires i 33. The circuit for clutch magnet I33 is from a power wire 633 via control switch 539, wire Mil to magnet let and then to return wire 838. The circuit for clutch magnet i3& is from power wire i353 via control switch Ml, wire M2 to magnet i3l, then to return wire Q38. The circuit for magnet I32 is from power wire 533 via control switch M3, wire to the switch member of contactor 928, then by wire M5 to magnet i3? and then to return wire For operating the brake as on hoist drum 23 of draw works W, the weight 5051 hung on brake lever 53 holds the hoist drum stationary. Gpposing this and to vary the braking pressure, the armature of a variable force magnet M6 is linked to a suitable crank or lever arm on brake shaft 33. The magnet t lt has tap wires i l'i connected to a rheostat M3 for varying the ampere turns of the magnet and thus varying the force exerted by its armature on the brake linkage. The circuit for the brake magnet is from a power wire 133 to rheostat i 33, tap wires Ml, magnet Md and then returning to common wire 638. Similarly for drum 39 of draw works a weight hung on brake lever 52 holds the hoist drum and its load. A variable force magnet M9 is linked to brake shaft 58. The circuit for brake magnet Me is from power wire to rheostat tap wire 95H, magnet M9 and then to the return line of power wires E33.

it is apparent that by means of the electromagnet system herein described, the two draw works ll and 2B and their respective motors i8 and 2i may be controlled and operated either individually or both together from any position in or near the derrick. Moreover either draw works may be controlled and operated manually by leaving open the appropriate control switches so that the magnets may not be energized.

As shown in Figures 4 and 5, like flexibility for the system ofligure '2 is provided by inserting clutches between the air cylinder linkage and the linkage for the draw works clutches and brake. Thus for draw works Bil the end of brake shaft 56 has a clutch H53 having a crank arm II53 to which is clevised the piston of cylinder Similarly, the pedal 65 is secured to a rock shaft I53 which is linked to yoke lever 33 for moving sloping jaw clutch 44; and a clutch lie on the end of rock shaft i54 has a crank arm I85 which is linked to the piston al of air cylinder lit. (lorrespondingly, pedal 89 is on rock shaft 118i which is connected by clutch 932 to cylinder Hi2. It will be seen that when clutches $152, 479 and it? are open the draw works linkage is disconnected from the air cylinders 55, I32 and H4 so that the draw works clutches and brakes must be manually operated; But when clutches i52, I19 and 582 are closed, the draw works. clutches and brakes may be power operated.

The main air valve 583 at the tank 9I controls the air supply to the pedal operated control valves of draw works i! and the air cylinders of draw works 20. The plain valves I84, I85 and I86 in the pipes 98, I03 and H5 respectively enable cutting out any or all of the air cylinders oi draw works 25.

It is not uncommon that a clutchbe inadvertently moved into engagement with its sprocket when the hoist drum of a draw works is rotating at appreciable speed to lower 1. e. unwinding line 63. The effect frequently is disastrous resulting usually in breakage of chain or sprocket or clutch or in bent shaft or drum shaft or other expensive damage and delay. To obviate this I provide the interlock shown in Figures 7 and 8.

A cam l55 is mounted on drum shaft 25 of draw works H or can. be drivenby a pulley on the drum shaft by a belt 956. The cam has a plurality of projections 65? for moving a'cam lever Mill. The lever may swing in either direction between two magnets W2 and i533 respectively,

so that when cam 555 is rotated in the direction oi arrow E56, a cam projection 851 encounters the roller end of cam lever I58 and swings the other end of the cam lever toward magnet i452 into its magnetic field, the camlever I58 serving as armature for the magnet. If the magnet not is energized its pull will swing the cam lever farther until the roller 159 is carried out of the path of the projections Hit, the cam lever being held against the magnet free and clear of the cam I55. Likewise when cam E55 rotates in the direction opposite to arrow I6 5, the cam lever 65B isswung towards magnet 963 and if the latter'is energized the cam lever will be pulled and held against the magnet clear of cam E55.

The lower end of cam lever 658 is provided with a switch member for contacting segmental contacts I55 when the cam lever moves toward mag- 40 net I62. The switch I65 controls an interceptor to. A spring magnet I65 the armature of which is linked to a pivoted intercepter Mil. This interceptor is positioned to intercept the clutch-pedals 58 and ti against downward movement when the magnet 45 I is energized thereby preventing operation of the clutches 3d and 35. This also prevents movement of air valves or electric switches which may be linked to the pedals arid thus prevent power operation of' the clutches of draw works I i58 normally holds the interceptor it? clear of the clutch pedals unless or until the interceptor magnet 166 is energized.

On the brake shaft to of the draw works ii! is a switch lever' H59 which may contact switch seg- 65 ments Illl when the brake lever 55 is'moved in the direction of easing or freeing the brake pressure on hoist drum 25. But when the brake lever is placed to hold the hoist drum stationary the switch lever I59 does not-contact the segments 60' H5 and the electrical circuit which they control is open.

The electrical circuit for the interlock is as follows: aswitch ill is connected to wires iii of Figure 2 or to wires I33 of Figure 3. A wire H2 osleads from switch Hi to cam switch I55 then by wire We to interceptor magnet E55 and then to return wire M5 to line switch iii. The circuit for magnets I52 and lttl is from wire 852 to magnet I52 then wire We to magnet L53 then 7 by wire ill to brake lever switch H0 then by wire we to return wire we. 7

Operation of the interlock is as follows: 'The driller may move brake lever 55 slightlyato lessen the brake pressure and permit hoist drum 25 to rotate slowly in the direction of arrow 656 which pulling interceptor is the direction for lowering the load on block,

Ml. If this movement is not sumcient to move switch lever Q59 into contact with switch no then clutch shifting may be accomplished but only when the hoist drum moves very slowly.

Meanwhile the projections i5! on cam H55 have caused cam lever l58 to swing towards the un energized magnet 552 but the slowness of the cam G55 and the restrant of spring H58 prevent the cam lever swinging far enough to close switch H55. But when the brake lever, 50 is moved iarther to permit the hoist drum to lower faster and switch lever I59 contacts switch 9705; then magnets i152 and I53 are energized, the camlever 058 as the armature is pulled firmly by magnet H52 to clear cam 655 and to close switch i156 whereupon interceptor magnet E55 is energized, it? into position to intercept foot pedals 58and iii thereby preventing closing clutches 5d and 35. When the drum rotation is in the direction for hoisting, that is, opposed to arrow 55%, then the cam 555 will cause cam lever 958 to swing towards magnet H53 and upon brake lever B59 closing switch H5 then magnet i533 will be energized. This will exert magnet pull on the cam lever and hold it clear of cam I155. But interceptor magnet 56 will not be energized and the clutch shifting will not be affected or hindered.

Figure i i shows pedal and brake lever opera tion of the switches that control the magnets of Figure 3. Thus inserted in wire M 5 in series with switch M5 is circular switch Miter which is linked to pedal H of draw works ll. Downward draw works 25. Also brake shaft 69 of draw works 6? may have sprocket IBl connected by chain 988 to a sprocket on rheostat I50 for operating brake magnet 39 of draw works 20. When the brake lever 50 ismoved in the direction of the arrow 58a. the brake pressure on hoist drum 26 is lessened and at the same time rheostat N0 is moved to close the circuit to brake magnet M9 for hoist drum 35. .First all the resistance is in series with a portion of the magnet windings then resistance is cut out and more windings o! the magnet are cut into the circuit.

Although I have described several specific embodiments of my invention, it will be obvious to those skilled in the art, that various modifica- -tions may be made in the details of construction,

pair of hoist mechanisms; a common load line in cooperative relation with both hoists, each of said mechanisms including a source of power; as well as a variable ratio transmission between the source of power and the corresponding hoist; and a common means for varying the ratio of both transmissions in unison.

2. In apparatus of the character described, a power hoist having a source of power, a variable ratio transmission for the hoist, means iorwary= ing said ratio, and means responsive to heavy load conditions imposed upon the source of power during low ratio operation, to prevent increasing the ratio of transmission.

' 3. In apparatus of the character described, a

hoist, an electric motor for driving said hoisha able ratio transmission for the hoist, means for varying said ratio, and means for preventing an increase in the ratio of transmission, responsive to heavy current consumption of the motor during low ratio operation.

4. In apparatus of the character described, a hoist, an electric motor for driving said hoist, a variable ratio transmission for the hoist, means for varying said ratio, and an interlock means between the motor and said ratio varying means, and responsive to load conditions of the motor.

5. In apparatus of the character described, a pair of hoists, a common line in cooperative relation with both hoists, a pair of sources of powmechanism.

er, respectively one for each hoist, means for varying the ratio of transmission between each source of power and the corresponding hoist,

manual means for controlling the ratio varying means for one hoist, and power means controlled by said manual means, for controlling the ratio varying means for the other hoist.

ii. In apparatus of the character described, a pair of hoists, a common line in cooperative relation with both hoists, a pair of sources of power, respectively one for each hoist, means for varying the ratio of transmission between each source of power and the corresponding hoist, electromagnetic means for controlling each ratio varying means, and a common manual means for operating both of said ratio controlling means.

7. In apparatus having two hoist mechanisms, each mechanism including a source of power,

- as well as a transmission mechanism for each source of power, and a plurality of clutches ar= ranged optionally to connect the source of power to the mechanism so that the ratio of transmission can be varied; the combination therewith of a common load line, and means whereby the corresponding clutches of both mechanisms can be simultaneously operated.

8. In apparatus having two hoist mechanisms, each mechanism including a source of power, as well as a transmission mechanism for each source of power, and a plurality of clutches arranged optionally to connect the source or power to the mechanism so that the ratio oitransmission can be varied; the combination therewith of a common load line, means for manually controlling the clutches of one mechanism, and power means controlled by said manual means, for operating the clutches of the other mechanism.

9. In apparatus having two hoist mechanisms, each mechanism including a source of power, as well as a transmission for each source of hower, and a brake for each mechanism; the combination therewith of a common load line, a crown block for confining the direction of hoisting substantially in a vertical direction, means for manually controlling the brake for one mechanism, and power means controlled by said manual means for operating the brake for the other ering operation.

12. In a hoist apparatus, a source of power for the apparatus, a clutch mechanism for connecting the source of power to the hoist, a brake mechanism therefor, and means for blocking the clutch mechanism against clutching movement, responsive to rapid lowering operation while the brake mechanism is at least partially released.

13. In a hoist apparatus, a source of power for the apparatus, a clutch mechanism for connecting the source of power to the hoist, and speed responsive means for maintaining the clutch mechanism against clutching movement during rapid lowering operation.

14. The combination as set forth in claim 13, in whichthe speed responsive means includes a penduious arm, and a cam driven by the hoist for oscillating the arm.

15. The combination as set forth in claim 13, in which the speed responsive means includes a pendulous arm, a cam driven by the hoist for oscillating the arm, and means active when the arm swings through a suflicient amplitude, to hold said arm out of the path of the cam.

16. The combination as set forth in claim 13, in which the speed responsive means includes a pendulous arm, a cam driven by the hoist for oscillating the arm, contacts controlled by the arm when its swing reaches a definite amplitude, and means for holding the arm in contact controlling position when said amplitude is reached.

l'l. In apparatus of the character described, a power hoist, a variable ratio transmission for the hoist, an electric motor connected to said transmission, and means responsive to an increase of load current supplied to the motor during low ratio operation, to prevent increasing the ratio of transmission, comprising an electromagnet and a current responsive relay for energizing said electromagnet.

18. In apparatus of the character described, a power operated hoist, a brake mechanism for holding the hoist against lowering movement and for permitting slow lowering, a clutch mechanism for rendering the hoist effective for raising operation, and means, responsive to an easing of! of the brake during lowering for preventing clutch- ,ing movement of the clutch mechanism.

19. In apparatus of the character described, a power operatedhoist, a brake mechanism for holding the hoist against lowering movement and for permitting slow lowering, a clutch mechanism for rendering the hoist effective for raising operation, and means, responsive to an easing off of the brake during lowering for preventing clutching movement of the clutch mechanism, comprising a circuit controller, and an electromagnet controlled thereby, said circuit controller being connected to the brake mechanism.

' 20. In apparatus of the character described, a power operated hoist, a brake mechanism for holding the hoist against lowering movement and ing movement of the clutch mechanism, comprising a circuit controller, an electromagnet controlled thereby, said circuit controller being connected to the brake mechanism, and another cir-.

cuit controller for the electromagnet, responsive selectively to fast lowering motion of the hoist.

21. In apparatus of the character described, a hoist mechanism, an electric motor for driving said mechanism, means for varying the ratio of the motor speed to the hoist speed, electromagnet-i0 means for controlling said ratio varyirig 6 egooeeoo "means, means for applying a braking force for netic for controlling said ratio vng the hoist, and. electromagnetic means for varying means, and means responsive to heavy load comthe brake pressure, and opposed to said force. ditions of the motor during low ratio operation.

22. In apparatus of the character described, a for rendering the electx'omegnetic means inefieo= 5 hoist mechanism, an electric motor for driving time for increasing the mtio. I 5

said mechanism, means for'verying the ratio of the motor speed to the hoist speed, eleotz'omag FRERIC W. 

